Resin composition, prepreg and their uses

ABSTRACT

A vinyl-compound-based resin composition containing a terminal vinyl compound (a) of a bifunctional phenylene ether oligomer having a polyphenylene ether skeleton, a specific maleimide compound (b), a naphthol aralkyl type cyanate ester resin (c) and a naphthalene-skeleton-modified novolak type epoxy resin (d) for a high-multilayer and high-frequency printed wiring board, which resin composition is excellent in varnish shelf life at low temperature and does not show a decrease in multilayer moldability, heat resistance after moisture absorption, electrical characteristics and peel strength even in a winter period and for a long period of time, and a prepreg, a metal-foil-clad laminate and a resin sheet each of which uses the above resin composition.

This application is a divisional of application Ser. No. 12/379,042filed Feb. 11, 2009, U.S. Pat. No. 8,748,541.

FIELD OF THE INVENTION

The present invention relates to a resin composition excellent in peelstrength, heat resistance after moisture absorption and electricalcharacteristics and a prepreg, a metal-foil-clad laminate and a resinsheet, each of which uses the above resin composition. The resincomposition is suitably used for a mother board and a semiconductorplastic package having a semiconductor chip mounted thereon, as a resincomposition for use in a printed wiring board for lead-free solderingreflow, high frequency and high multilayer.

BACKGROUND OF THE INVENTION

In recent years, information terminal devices such as personal computersand servers and telecommunications devices such as internet routers andoptical communication are required to process mass data at high speedand the speed and frequency of electric signals are increasinglybecoming higher. Accordingly, laminates for printed wiring boards to beused for these devices are required to have a lower dielectric constantand a lower dielectric loss tangent, in particular to have a lowerdielectric loss tangent, for the purpose of coping with the demand forhigh frequency.

For coping with these demands, conventionally, a cyanate ester resin(see, for example JP-A-2005-120173) and a polyphenylene ether resin(see, for example JP-A-2005-112981) are known as a resin for laminatesfor high frequency uses. As an epoxy resin to be used for high frequencyuses, many reports say a biphenyl aralkyl type novolak epoxy resin isexcellent in dielectric characteristics (see, for example,JP-A-10-237162, JP-A-2002-179761 and JP-A-2007-224162).

However, the above-mentioned biphenyl aralkyl novolak type epoxy resinhas a problem in that a solution article thereof, which is obtained bydissolving the biphenyl aralkyl type novolak epoxy resin in an organicsolvent, is poor in shelf life. As for the shelf life of a solutionarticle of a resin composition, it is generally necessary that a solidcontent does not precipitate for at least three months when it is storedat 5° C. On the other hand, the solution product of the biphenyl aralkyltype novolak epoxy resin shows a precipitation of a solid content in ashort period of time or about two weeks when stored at 5° C. Therefore,the stability of the quality of a prepreg or laminate which uses avarnish obtained by dissolving a resin composition containing thebiphenyl aralkyl type novolak epoxy resin is a large problem.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide avinyl-compound-based resin composition for a printed wiring board forhigh multilayer structure and high frequency, which resin composition isexcellent in varnish shelf life at low temperature and does not show adecrease in multilayer moldability, heat resistance after moistureabsorption, electrical characteristics and peel strength in a winterperiod and during a long period of time, and a prepreg, ametal-foil-clad laminate and a resin sheet each of which uses the aboveresin composition. In the present invention, the shelf life is judged onthe basis of the occurrence or non-occurrence of a precipitation of asolid content in a solution of a resin composition, i.e., varnish, afterthe solution is stored at a predetermined temperature for apredetermined period of time.

The present inventors have made diligent studies for achieving the aboveobject and as a result found the following. By mixing a vinyl compoundhaving a structure which is obtained by vinyl benzylation of a terminalof a bifunctional phenylene ether oligomer having a specific numberaverage molecular weight and having a polyphenylene ether skeleton, witha maleimide compound, a naphthol aralkyl type cyanate ester resin and anaphthalene-skeleton-modified novolak type epoxy resin in a specificmixing equivalent ratio, further adding a phosphazene compound having nofunctional group or a bromine compound having no functional group to themixture and further incorporating an inorganic filler jointly, thethus-obtained resin composition is excellent in varnish shelf life andimproved in electrical characteristics, peel strength and thermaldecomposition temperature without any decrease in multilayer moldabilityand heat resistance after moisture absorption. On the basis of the abovefinding, the present inventors have arrived at the present invention.

That is, the present invention provides a resin composition containing avinyl compound (a) having a structure obtained by vinyl benzylation of aterminal of a bifunctional phenylene ether oligomer having apolyphenylene ether skeleton, a specific maleimide compound (b), anaphthol aralkyl type cyanate ester resin (c) and anaphthalene-skeleton-modified novolak type epoxy resin (d).

Preferably, the resin composition provided by the present inventionfurther contains a specific cyclophosphazene compound or a brominatedpolycarbonate as a flame retardant and an inorganic filler.

In the resin composition provided by the present invention, morepreferably, the maleimide compound (b) is a bismaleimide resin, thecyclophosphazene compound is a cyclophosphazene resin containing a cyanogroup and the inorganic filler is a spherical silica having an averageparticle diameter of 3 μm or less.

The present invention further provides a prepreg obtained byimpregnating the above resin composition into a glass woven fabric andsemi-curing the resultant fabric and a metal-foil-clad laminate obtainedby disposing metal foil(s) on one surface or both surfaces of oneprepreg as obtained above or a stack of at least two prepregs asobtained above and laminate-molding the resultant set.

The present invention furthermore provides a varnish comprising theabove resin composition and an organic solvent. The present inventionstill further provides a resin sheet obtained by applying the abovevarnish to a metal foil or a film.

EFFECT OF THE INVENTION

A solution comprising the resin composition provided by the presentinvention and an organic solvent, i.e., varnish, is free from aprecipitation of a solid content even in a long-term storage at a lowtemperature. Therefore, it is excellent in shelf life as a varnish. Aprinted wiring board which uses a prepreg or metal-foil-clad laminateobtained from the above resin composition is stable in properties suchas multilayer moldability, heat resistance after moisture absorption,peel strength, electrical characteristics, dimensional stability andmoldability through a winter manufacturing period. Therefore, the resincomposition provided by the present invention is suitable for a printedwiring board material for a highly multilayered and high frequencyprinted wiring board. Its industrial practicality is remarkable high.

DETAILED DESCRIPTION OF THE INVENTION

The vinyl compound (a) represented by the formula (1), used in thepresent invention, is not specially limited so long as it is a vinylcompound of the formula (1) wherein —(O—X—O)— represents a structuredefined by the formula (2) or the formula (3) in which R₁, R₂, R₃, R₇and R₈ are the same or different and represent a halogen atom, an alkylgroup having 6 or less carbon atoms or a phenyl group, R₄, R₅, R₆, R₉,R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅ and R₁₆ are the same or different andrepresent a hydrogen atom, a halogen atom, an alkyl group having 6 orless carbon atoms or a phenyl group, and -A- represents a linear,branched or cyclic bivalent hydrocarbon group having 20 or less carbonatoms, —(Y—O)— represents an arrangement of a structure defined by theformula (4) or a random arrangement of at least two kinds of structuresdefined by the formula (4), in which R₁₇ and R₁₈ are the same ordifferent and represent a halogen atom, an alkyl group having 6 or lesscarbon atoms or a phenyl group and R₁₉ and R₂₀ are the same or differentand represent a hydrogen atom, a halogen atom, an alkyl group having 6or less carbon atoms or a phenyl group, and each of a and b is aninteger of 0 to 100, provided that at least one of a and b is not 0.Further, the resin composition of the present invention can contain atleast two kinds of vinyl compounds (a) which are different in structurefrom each other.

Examples of -A- in the formula (3) include bivalent organic groups suchas methylene, ethylidene, 1-methylethylidene, 1,1-propylidene,1,4-phenylenebis(1-methylethylidene),1,3-phenylenebis(1-methylethylidene), cyclohexylidene, phenylmethylene,naphthyl methylene and 1-phenylethylidene. -A- in the formula (3) is notlimited to these examples.

Among the vinyl compounds (a) in the present invention, a vinyl compound(a) of the formula (1) in which R₁, R₂, R₃, R₇, R₈, R₁₇ and R₁₈represent an alkyl group having 3 or less carbon atoms and R₄, R₅, R₆,R₉, R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅, R₁₆, R₁₉ and R₂₀ represent a hydrogenatom or an alkyl group having 3 or less carbon atoms is preferred. Inparticular, a vinyl compound (a) of the formula (1), in which —(O—X—O)—represented by the formula (2) or the formula (3) is a structure of theformula (8), the formula (9) or the formula (10), and —(Y—O)—represented by the formula (4) is an arrangement of a structure of theformula (11) or the formula (12) or a random arrangement of a structureof the formula (11) and a structure of the formula (12), is morepreferred.

wherein R₁₁, R₁₂, R₁₃ and R₁₄ are the same or different and represent ahydrogen atom or a methyl group, and -A- is a linear, branched or cyclicbivalent hydrocarbon group having 20 or less carbon atoms.

wherein -A- is a linear, branched or cyclic bivalent hydrocarbon grouphaving 20 or less carbon atoms.

The number average molecular weight, calculated as polystyrene accordingto a GPC method, of the vinyl compound (a) is preferably in the range offrom 500 to 3,000. When the number average molecular weight is smallerthan 500, a coating film obtained from the resin composition is apt tobe sticky. When it exceeds 3,000, the solubility into a solventdecreases. A process for producing the vinyl compound (a) is notspecially limited. For example, it can be produced by vinylbenzyletherification of a terminal phenolic hydroxyl group of a bifunctionalphenylene ether oligomer obtained by oxidative coupling of abifunctional phenol compound and a monofunctional phenol compound.

The bifunctional phenylene ether oligomer can be produced, for example,by dissolving the bifunctional phenol compound, the monovalent phenolcompound and a catalyst in a solvent and then introducing oxygen intothe resultant solution under heat with stirring. Examples of thebifunctional phenol compound include2,2′,3,3′,5,5′-hexamethyl-(1,1′-biphenol)-4,4′-diol,4,4′-methylenebis(2,6-dimethylphenol), 4,4′-dihydroxyphenylmethane and4,4′-dihydroxy-2,2′-diphenylpropane. The bifunctional phenol compound isnot limited to these examples. Examples of the monofunctional phenolcompound include 2,6-dimethylphenol and 2,3,6-trimethylphenol. Themonofunctional phenol compound is not limited to these examples. Thecatalyst is, for example, a combination of a copper salt and an amine.Examples of the copper salt include CuCl, CuBr, CuI, CuCl₂ and CuBr₂.Examples of the amine include n-butylamine, n-butyldimethylamine,N,N′-dit-butylethylenediamine, pyridine,N,N,N′,N′-tetramethylethylenediamine, piperidine and imidazole. Thecatalyst is not limited to these examples. Examples of the solventinclude toluene, methanol, methyl ethyl ketone and xylene. The solventis not limited to these examples.

As for a method of the vinylbenzyl etherification of a terminal phenolichydroxyl group of the bifunctional phenylene ether oligomer, forexample, it can be carried out by dissolving the bifunctional phenyleneether oligomer and vinylbenzyl chloride in a solvent, adding a base tothe thus-obtained solution under heat with stirring to allow thecomponents to react and then solidifying a resin. Examples of thevinylbenzyl chloride include o-vinylbenzylchloride,m-vinylbenzylchloride, p-vinylbenzylchloride and mixtures of these. Thevinylbenzyl chloride is not limited to these examples.

Examples of the base include sodium hydroxide, potassium hydroxide,sodium methoxide and sodium ethoxide. The base is not limited to theseexamples. An acid can be used in order to neutralize the base whichremains after the reaction.

Examples of the acid include hydrochloric acid, sulfuric acid,phosphoric acid, boric acid and nitric acid. The acid is not limited tothese examples. Examples of the solvent for the reaction includetoluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone,dimethylformamide, dimethylacetamide, methylene chloride and chloroform.The solvent for the reaction is not limited to these examples. As amethod of the solidification of the resin, a method in which the solventis evaporated to dry and solidify the resin and a method in which areaction liquid is mixed with a poor solvent to precipitate the resincan be adopted. The method of the solidification is not limited to thesemethods.

The amount of the vinyl compound (a) is preferably 30 to 95 parts byweight, particularly preferably 50 to 80 parts by weight, in 100 partsby weight of a resin solid content in the resin composition. When theamount of the vinyl compound (a) is not in the above range, a problemabout electrical characteristics or reactivity occurs.

The maleimide compound (b) containing at least two maleimide groups in amolecule, represented by the formula (5), used in the present inventionis not specially limited so long as it is a maleimide compound of theformula (5) in which Z is an organic group having 200 or less carbonatoms which may contain an oxygen atom, a sulfur atom, a phosphorus atomand/or a nitrogen atom, and c is an integer of 2 to 20. When the numberof maleimide groups in a molecule is increased, an unreacted maleimidegroup is apt to remain at the time of curing. When maleimide equivalentbecomes large, reactivity becomes poor. For these reasons, preferably, cis 2 to 10 and the maleimide equivalent is 2,000 or less (g/maleimidegroup). More preferably, c is 2 to 10 and the maleimide equivalent is1,000 or less (g/maleimide group). Most preferably, c is 2 to 10 and themaleimide equivalent is 500 or less (g/maleimide group). Z is preferablya hydrocarbon group, an organic group comprising a carbon atom, ahydrogen atom and an oxygen atom, an organic group comprising a carbonatom, a hydrogen atom and a nitrogen atom or an organic group comprisinga carbon atom, a hydrogen atom, a nitrogen atom and an oxygen atom.

Examples of the maleimide compound (b) include1,1′-(methylenedi-4,1-phenylene)bismaleimide,N,N′-m-phenylenebismaleimide,2,2′-bis-[4-(4-maleimidophenoxy)phenyl]propane,3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethane bismaleimide,4-methyl-1,3-phenylenebismaleimide, 4,4′-diphenyletherbismaleimide,4,4′-diphenylsulfone bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene,1,3-bis(4-maleimidophenoxy)benzene, N,N′-4,4′-diphenyletherbismaleimide, N,N′-4,4-dicyclohexylmethane bismaleimide, N,N′-ethylenebismaleimide, N,N′-butylene bismaleimide, N,N′-hexamethylenebismaleimide, N,N′-diphenylcyclohexane bismaleimide,1,6-bismaleimido-(2,2,4-trimethyl)hexane, 1,6-bismaleimidohexane,1,11-bismaleimidodiethylene glycol, 1,4-bis(4-maleimidophenoxy)ethane,1,4-bis(4-maleimidophenoxy)propane, 1,4-bis(4-maleimidophenoxy)butane,1,4-bis(4-maleimidophenoxy)hexane, tris(4-maleimidophenyl)amine,bis(4-maleimidophenyl)methylamine, bis(4-maleimidophenyl)phenylamine,N,N′-4,4′-diphenylsulfone bismaleimide, N,N′-4,4′-diphenylsulfidebismaleimide, a polycondensate of aniline, formaldehyde and maleicanhydride, poly(oxy-1,4-butanediyl), andα-[4-(2,5-dihydro-2,5-dioxo-1H-pyrrole-1-yl)benzoyl]oxy-ω-[[4-(2,5-dihydro-2,5-dioxo-1H-pyrrole-1-yl)benzoyl]oxy]-.The maleimide compound (b) is not limited to these examples. Themaleimide compound (b) can be used singly or at least two maleimidecompounds (b) can be used in combination. Bismaleimide is preferred interms of the reactivity with the vinyl compound and heat resistanceafter moisture absorption.

The amount of the maleimide compound (b) used in the present inventionis preferably in the range of from 0.01 to 20 parts by weight,particularly preferably 1 to 15 parts by weight, in 100 parts by weightof a resin solid content in the resin composition. When the amount ofthe maleimide compound (b) is not in the above range, the reactivity ishigh and electrical characteristics and heat resistance after moistureabsorption are decreased in some cases.

The cyanate ester resin (c) used in the present invention is notspecially limited so long as it is selected from cyanate ester resinsrepresented by the formula (6) and prepolymers thereof. The cyanateester resin (c) represented by the formula (6) is obtained bycondensation of a cyanic acid and a naphthol aralkyl resin which isobtained by reaction between a naphthol such as α-naphthol or β-naphtholand p-xylyleneglycol, α,α′-dimethoxy-p-xylene,1,4-di(2-hydroxy-2-propyl)benzene or the like. The process for producingthe cyanate ester resin (c) is not specially limited. The cyanate esterresin (c) can be produced by any method known as a cyanate estersynthesis method.

Specifically, for example, the cyanate ester resin (c) is obtained byreacting a naphthol aralkyl resin represented by the formula (13) and acyanogen halide in an inactive organic solvent in the presence of abasic compound. Further, it is possible to adopt a synthesis method inwhich a salt of a similar naphthol aralkyl resin and a basic compound isformed in a solution containing water and then the salt is reacted witha cyanogen halide in a two-phase interface reaction, therebysynthesizing the cyanate ester resin (c). The amount of the cyanateester resin (c) used in the present invention is preferably in the rangeof from 1 to 25 parts by weight, particularly preferably 3 to 15 partsby weight, in 100 parts by weight of a resin solid content in the resincomposition. When the amount of the cyanate ester resin (c) is not inthe above range, electrical characteristics and heat resistance aftermoisture absorption are decreased in some cases.

wherein R represents a hydrogen atom or a methyl group and n is from 1to 10.

wherein R represents a hydrogen atom or a methyl group and n is from 1to 10.

The naphthalene-skeleton-modified novolak type epoxy resin (d) used inthe present invention is an epoxy resin having a repeating structure ofthe formula (7) and having a naphthalene skeleton in a molecule,

wherein R₂₁ represents an alkyl group having 1 to 6 carbon atoms, R₂₂represents an alkyl group having 1 to 6 carbon atoms or an alkoxy grouphaving 1 to 6 carbon atoms, B is a direct bond (that is, a naphthalenering directly bonds to a benzene ring of an adjacent repeating unit) oran alkylene group having 1 to 6 carbon atoms, and m is from 1 to 10.

The naphthalene-skeleton-modified novolak type epoxy resin (d) ischaracterized in that it is excellent in heat resistance, flameretardancy, moisture resistance and dielectric characteristics ascompared with general-purpose epoxy resins, since a naphthalene skeletonis given in a high density into a molecule. In particular, it ispreferred that the above epoxy resin (d) has a repeating structurerepresented by the formula (14). Specifically, HP5000 and EXA9900,supplied by DIC Corporation, can be used as the epoxy resin (d). Thetotal amount of the aforementioned cyanate ester resin (c) and thenaphthalene-skeleton-modified novolak type epoxy resin (d) is preferably3 to 30 parts by weight, particularly preferably 5 to 25 parts byweight, in 100 parts by weight of a resin solid content in the resincomposition. When it is not in the above range, peel strength,electrical characteristics or heat resistance after moisture absorptionare decreased in some cases.

wherein m is from 1 to 10.

A cyclophosphazene compound having a cyano group or a brominatedpolycarbonate resin is preferably used as a flame retardant in thepresent invention. These flame retardants are characterized in thatthese flame retardants are excellent in heat resistance, electricalcharacteristics and solvent solubility. The amount of thecyclophosphazene compound having a cyano group is preferably 10 to 30parts by weight, particularly preferably 15 to 25 parts by weight, per100 parts by weight of a resin solid content in the resin composition.When it is not in the above range, a problem is that flame retardancy orpeel strength is decreased. The molecular weight of the brominatedpolycarbonate resin is not specially limited. It is preferably 500 to2,000 as a weight average molecular weight. The content of bromine inthe brominated polycarbonate resin is preferably 30 to 80%. The amountof the brominated polycarbonate resin is preferably 5 to 25 parts byweight, particularly preferably 10 to 20 parts by weight, per 100 partsby weight of a resin solid content in the resin composition. When it isnot in the above range, a problem is that flame retardancy or peelstrength is decreased.

The inorganic filler used in the present invention is not speciallylimited so long as it is selected from general inorganic fillers forlaminates. Specifically, examples of the inorganic filler includesilicas such as natural silica, fused silica, synthetic silica,amorphous silica and hollow silica, molybdenum compounds such asmolybdenum oxide and zinc molybdate, zinc borate, zinc stannate,alumina, clay, kaolin, talc, calcined clay, calcined kaolin, calcinedtalc, mica, short glass fiber (fine powders of glasses such as E glassor D glass) and hollow glass. The inorganic filler can be used singly orat least two inorganic fillers can be used in combination.

The average particle diameter (D50) of the inorganic filler to be usedis not specially limited, while a mesoporous silica, a spherical fusedsilica, a spherical synthetic silica and a hollow spherical silica, eachof which has an average particle diameter (D50) of 0.1 to 3 μm, arepreferred in consideration of dispersibility. When the average particlediameter is not in the range of from 0.1 to 3 μm, a problem aboutflowing characteristic at the time of molding or a problem of breakageof a small-diameter drill bit in use occurs in some cases. The amount ofthe inorganic filler is not specially limited. It is preferably 10 to150 parts by weight, particularly preferably 20 to 100 parts by weight,per 100 parts by weight of a resin solid content in the resincomposition. When the amount of the inorganic filler is too large,moldability is decreased in some cases. For this reason, the amount ofthe inorganic filler is particularly preferably 100 parts by weight orless.

A silane coupling agent or a wetting and dispersing agent can be usedjointly with the inorganic filler. The silane coupling agent is notspecially limited so long as it is selected from silane coupling agentswhich are generally used for surface-treating inorganic substances.Specific examples of the silane coupling agent include aminosilanecoupling agents such as γ-aminopropyltriethoxysilane andN-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, epoxysilane couplingagents such as γ-glycidoxypropyltrimethoxysilane, vinylsilane couplingagents such as γ-methacryloxypropyltrimethoxysilane, cationic silanecoupling agents such asN-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilanehydrochloride, and phenylsilane coupling agents. The silane couplingagent can be used singly or at least two silane coupling agents can beused in combination, as required.

A curing accelerator can be jointly used in the resin composition of thepresent invention, as required, for properly adjusting a curing speed.The curing accelerator is not specially limited so long as it isselected from curing accelerators which are generally used as a curingaccelerator for the vinyl compound (a), the maleimide compound (b), thenaphthol aralkyl type cyanate ester resin (c) and thenaphthalene-skeleton-modified novolak type epoxy resin (d). Specificexamples thereof include organic metal salts such as copper, zinc,cobalt and nickel, imidazoles and derivatives thereof, tertiary amines,and radical polymerization initiators.

A cross-linking type curing agent can be added to the resin compositionof the present invention as required. The cross-linking type curingagent has an effect of increasing the fluidity of the resin compositionand improving copper foil peel strength. In particular, a cross-linkingcuring agent having good compatibility with a terminal vinyl compound ofa bifunctional phenylene ether oligomer having a polyphenylene etherskeleton is preferably used. Specific examples of the cross-linking typecuring agent include a polyfunctional vinyl compound such asdivinylbenzene, divinylnaphthalene or divinylbiphenyl, a vinylbenzylether compound synthesized by a reaction between phenol and vinylbenzylchloride, and an allyl ether compound synthesized by a reaction betweena styrene monomer, phenol and allyl chloride. Further, trialkenylisocyanurate, etc., is preferable. In particular, trialkenylisocyanurate having good compatibility is preferable. Especially,specifically, triallyl isocyanurate (TAIC) or triallyl cyanurate (TAC)is preferred. This is because these are excellent in moldability and alaminate excellent in copper foil peel strength can be obtained.

A polymerization inhibitor can be added to the resin composition of thepresent invention for increasing shelf life. The polymerizationinhibitor can be selected from generally-known polymerizationinhibitors. Examples thereof include quinones such as hydroquinone,methyl hydroquinone, p-benzoquinone, chloranil and trimethylquinone,aromatic diols, and di-t-butylhydroxytoluene.

A variety of high molecular weight compounds such as a differentthermosetting resin, a thermoplastic resin and an oligomer thereof, andelastomers, a different flame retardant compound, an additive and thelike can be further used in the resin composition of the presentinvention so long as the inherent properties of the resin compositionare not impaired. These are not specially limited so long as these areselected from those which are generally used. For instance, examples ofthe flame retardant compound include a bromine compound such as4,4-dibromobiphenyl, phosphoric acid ester, melamine phosphate, aphosphorus-containing epoxy resin, a nitrogen compound such as melamineor benzoguanamine, an oxazine-ring-containing compound and a siliconecompound. Examples of the additive include an ultraviolet absorber, anantioxidant, a photopolymerization initiator, a fluorescent brighteningagent, a photosensitizer, a dye, a pigment, a thickener, a lubricant, anantifoamer, a dispersing agent, a leveling agent and a brightener. Thesecan be used in combination as required.

The varnish provided by the present invention comprises theaforementioned resin composition and an organic solvent. The organicsolvent is not specially limited so long as it dissolves a mixture ofthe vinyl compound (a), the maleimide compound (b), the cyanate esterresin (c) and the epoxy resin (d). Specific examples thereof includeketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone;polar solvents such as dimethylacetamide and dimethylformamide; andaromatic hydrocarbon solvents such as toluene and xylene. The organicsolvent can be used singly or at least two organic solvents can be usedin combination. A procedure of dissolving the components for thepreparation of the varnish is not specially limited. It is possible todissolve the components in the above organic solvent and then mix them.Otherwise, it is also possible to mix all the components and thendissolve the resultant mixture in the organic solvent. The concentrationof a resin solid content in the varnish is preferably 55 to 70%,particularly preferably 60 to 65%. When it is not in the above range,the shelf life of the varnish or the impregnating ability of the varnishin a glass woven fabric worsens in some cases.

The glass woven fabric used in the present invention is typically Eglass, D glass, S glass, T glass, NE glass or quartz. The thickness ofthe glass woven fabric is not specially limited. A glass woven fabricfor a laminate, which has a thickness of 0.01 to 0.2 mm and, inparticular, which is subjected to super opening treatment or cloggingtreatment, is preferred in terms of dimensional stability. Further, aglass woven fabric subjected to surface-treatment with a silane-couplingagent, such as epoxysilane treatment or aminosilane treatment, ispreferably used in terms of heat resistance after moisture absorption.

A process of producing the prepreg of the present invention is notspecially limited so long as it is a method in which the prepreg isproduced by combining the aforementioned resin composition and the glasswoven fabric. Specifically, the resin composition of the presentinvention is impregnated into the glass woven fabric and the resultantglass woven fabric is dried, for example, at 130° C. to 180° C. forabout 3 to 20 minutes, thereby obtaining a prepreg which is in asemi-cured and B-staged state and has a resin amount of about 30 to 90%by weight. In the above resin amount, the amount of the inorganic filleris included. The impregnation can be carried out by a known method.There are a method in which the varnish of the present invention isimpregnated into the glass woven fabric and, in addition, a method inwhich the resin composition of the present invention is thermally moltenand the molten resin composition is impregnated into the glass wovenfabric.

The metal-foil-clad laminate provided by the present invention isobtained by laminate-molding in which the above prepreg is used.Specifically, a predetermined number of the above prepregs are stacked,copper foil (s) are provided on one surface or both surfaces of thestacked prepregs, and the copper foil(s) and the stacked prepregs arelaminate-molded, for example, at a temperature of 180 to 220° C. for aheating time of 100 to 300 minutes under a surface pressure of 20 to 40kg/cm², thereby obtaining a copper-clad laminate. The thickness of thecopper foil to be used is not specially limited. An electrolytic copperfoil having a thickness of 3 to 35 μm is preferably used. Theelectrolytic copper foil is not specially limited so long as it isselected from general electrolytic copper foils for laminates. Anelectrolytic copper foil having small mat surface roughness is preferredin consideration of a conductor loss in a high frequency region. As amethod of producing a multilayer board, for instance, copper foilshaving a thickness of 35 μm each are provided on both surfaces, onecopper foil on each surface, of one prepreg of the present invention,the copper foils and the prepreg are laminate-molded under the aboveconditions, then an inner layer circuit is formed, and the circuit issubjected to blacking treatment, to form an inner layer circuit board.Such inner layer circuit boards and the prepregs of the presentinvention are one by one disposed alternatively, copper foils aredisposed as outermost layers, and the circuit boards, the prepregs andthe copper foils are laminate-molded under the above conditions,preferably in vacuum, thereby obtaining a multilayer board.

The resin sheet provided by the present invention is obtained byapplying the aforementioned varnish to a base material, drying theapplied varnish and then separating or etching the base material.Examples of the base material include organic film base materials suchas polyethylene film, polypropylene film, polycarbonate film,polyethylene terephthalate film, ethylene tetrafluoroethylene copolymerfilm, a releasing film obtained by applying a releasing agent to thesurface of any one of these films, and polyimide film, conductive foilssuch as copper foil and aluminum foil, and plate-like base materialssuch as glass plate, SUS plate and FRP. As an application method, forexample, there is a method in which a solution of the resin compositionis applied to the base material with a bar coater, a die coater, adoctor blade, a baker applicator or the like and the solvent is removedby drying.

Drying conditions for removing the solvent by drying are not speciallylimited. When the drying is carried out at a low temperature, thesolvent is apt to remain in the resin composition. When the drying iscarried out at a high temperature, curing of the resin compositionadvances. Therefore, it is preferred that the drying is carried out at atemperature of 20° C. to 150° C. for 1 to 90 minutes. The thickness of aresin layer can be adjusted by the concentration of the resincomposition solution and the application thickness of the resincomposition solution. When the application thickness is large, thesolvent is apt to remain at the time of drying. Therefore, theapplication thickness of the resin composition solution is preferably0.1 to 500 μm.

The resin composition of the present invention can be used as aninsulating layer of a printed wiring board or a material for asemiconductor package. For example, a resin-attached copper foil can beprepared by applying a solution of the curable resin composition of thepresent invention in a solvent to a copper foil as a base material anddrying the applied solution. Further, a film for buildup, a dry filmsolder resist or a die attach film can be prepared by applying asolution of the curable resin composition of the present invention in asolvent to a separable plastic film as a base material and drying theapplied solution. The solvent can be dried and removed by heating at atemperature of 20° C. to 150° C. for 1 to 90 minutes. The curable resincomposition can be used in an uncured state only after removing solventby drying, and it can be also used in a semi-cured state, as required.

EXAMPLES

The present invention will be concretely explained with reference toExamples and Comparative Examples, hereinafter, while the presentinvention shall not be limited to these Examples.

Synthetic Example 1 Synthesis of Bifunctional Phenylene Ether Oligomer

9.36 g (42.1 mmol) of CuBr₂, 1.81 g (10.5 mmol) ofN,N′-di-t-butylethylenediamine, 67.77 g (671.0 mmol) ofn-butyldimethylamine and 2,600 g of toluene were charged into alongitudinally long reactor having a volume of 12 liters and equippedwith a stirrer, a thermometer, an air-introducing tube and baffleplates.The mixture was stirred at a reaction temperature of 40° C. A mixedsolution was obtained by dissolving 129.32 g (0.48 mol) of2,2′,3,3′,5,5′-hexamethyl-(1,1′-biphenol)-4,4′-diol, 878.4 g (7.2 mol)of 2,6-dimethylphenol, 1.22 g (7.2 mmol) ofN,N′-di-t-butylethylenediamine and 26.35 g (260.9 mmol) ofn-butyldimethylamine in 2,300 g of methanol in advance. The mixedsolution was dropwise added to the mixture in the reactor over 230minutes with stirring while bubbling was carried out with a nitrogen-airmixed gas having an oxygen concentration of 8% at a flow rate of 5.2L/min. After the completion of the addition, 1,500 g of water containing48.06 g (126.4 mmol) of tetrasodium ethylenediamine tetraacetatedissolved therein was added to the stirred mixture to terminate thereaction. An aqueous layer and an organic layer were separated. Then,the organic layer was washed with 1N hydrochloric acid aqueous solutionand then washed with pure water. The thus-obtained solution wasconcentrated to 50 wt % with an evaporator, to obtain 1,981 g of atoluene solution of a bifunctional phenylene ether oligomer compound(resin “A”). The resin “A” had a number average molecular weight of1,975, a weight average molecular weight of 3,514 and a hydroxyl groupequivalent of 990.

(Synthesis of Vinyl Compound)

833.40 g of the toluene solution of the resin “A”, 76.7 g of vinylbenzylchloride (trade name CMS-P; supplied by Seimi Chemical Co., Ltd.), 1,600g of methylene chloride, 6.2 g of benzyldimethylamine, 199.5 g of purewater and 83.6 g of 30.5 wt % NaOH aqueous solution were charged into areactor equipped with a stirrer, a thermometer and a reflux tube. Themixture was stirred at a reaction temperature of 40° C. The stirring wascarried out for 24 hours. Then, an organic layer was washed with 1Nhydrochloric acid aqueous solution and then washed with pure water. Thethus-obtained solution was concentrated with an evaporator, and theconcentrated solution was dropwise added to methanol to obtain a solid.The solid was recovered by filtering, and the recovered solid was driedin vacuum to obtain 450.1 g of a vinyl compound “B”. The vinyl compound“B” had a number average molecular weight of 2,250, a weight averagemolecular weight of 3,920 and a vinyl group equivalent of 1,189 g/vinylgroup.

Synthetic Example 2 Synthesis of Bifunctional Phenylene Ether Oligomer

3.88 g (17.4 mmol) of CuBr₂, 0.75 g (4.4 mmol) ofN,N′-di-t-butylethylenediamine, 28.04 g (277.6 mmol) ofn-butyldimethylamine and 2,600 g of toluene were charged into alongitudinally long reactor having a volume of 12 liters and equippedwith a stirrer, a thermometer, an air-introducing tube and baffleplates.The mixture was stirred at a reaction temperature of 40° C. A mixedsolution was obtained by dissolving 129.3 g (0.48 mol) of2,2′,3,3′,5,5′-hexamethyl-(1,1′-biphenol)-4,4′-diol, 233.7 g (1.92 mol)of 2,6-dimethylphenol, 64.9 g (0.48 mol) of 2,3,6-trimethylphenol, 0.51g (2.9 mmol) of N,N′-di-t-butylethylenediamine and 10.90 g (108.0 mmol)of n-butyldimethylamine in 2,300 g of methanol in advance. The mixedsolution was dropwise added to the mixture in the reactor over 230minutes with stirring while bubbling was carried out with a nitrogen-airmixed gas having an oxygen concentration of 8% at a flow rate of 5.2L/min. After the completion of the addition, 1,500 g of water containing19.89 g (52.3 mmol) of tetrasodium ethylenediamine tetraacetatedissolved therein was added to the stirred mixture to terminate thereaction. An aqueous layer and an organic layer were separated. Theorganic layer was washed with 1N hydrochloric acid aqueous solution andthen washed with pure water. The thus-obtained solution was concentratedto 50 wt % with an evaporator, to obtain 836.5 g of a toluene solutionof a bifunctional phenylene ether oligomer compound (resin “C”). Theresin “C” had a number average molecular weight of 986, a weight averagemolecular weight of 1,530 and a hydroxyl group equivalent of 471.

(Synthesis of Vinyl Compound)

836.5 g of the toluene solution of the resin “C”, 162.6 g of vinylbenzylchloride (trade name CMS-P; supplied by Seimi Chemical Co., Ltd.), 1,600g of methylene chloride, 12.95 g of benzyldimethylamine, 420 g of purewater and 178.0 g of 30.5 wt % NaOH aqueous solution were charged into areactor equipped with a stirrer, a thermometer and a reflux tube. Themixture was stirred at a reaction temperature of 40° C. The stirring wascarried out for 24 hours. Then, an organic layer was washed with 1Nhydrochloric acid aqueous solution and then washed with pure water. Thethus-obtained solution was concentrated with an evaporator, and theconcentrated solution was dropwise added to methanol to obtain a solid.The solid was recovered by filtering, and the recovered solid was driedin vacuum to obtain 503.5 g of a vinyl compound “D”. The vinyl compound“D” had a number average molecular weight of 1,187, a weight averagemolecular weight of 1,675 and a vinyl group equivalent of 590 g/vinylgroup.

Synthetic Example 3 Synthesis of α-Naphthol Aralkyl Type Cyanate EsterResin

103 g (OH group 0.47 mol) of an α-naphthol aralkyl resin represented bythe formula (15) (SN485, OH group equivalent: 219 g/eq., softeningpoint: 86° C., supplied by Nippon Steel Chemical Co., Ltd.) wasdissolved in 500 ml of chloroform. Then, 0.7 mol of triethylamine wasadded and mixed with the resultant solution. The mixture was dropwiseadded to 300 g of a chloroform solution of 0.93 mol of cyanogen chlorideat −10° C. over 1.5 hours. The resultant mixture was stirred for 30minutes. Then, a mixed solution of 0.1 mol of triethylamine and 30 g ofchloroform was dropwise added to the stirred mixture and the mixture wasstirred for 30 minutes to complete the reaction. A hydrochloride oftriethylamine to be generated was separated by filtering, to obtain afiltrate. The filtrate was washed with 500 ml of 0.1N hydrochloric acidand then washing with 500 ml of water was repeated four times. Then, achloroform layer of chloroform/water mixed solution was extracted byliquid-separation treatment. Sodium sulfate was added to the chloroformsolution to carry out dehydration treatment. The sodium sulfate wasseparated by filtering. Then, the resultant solution was evaporated at75° C. and then further deaerated under reduced pressure at 90° C., toobtain a blackish brown solid α-naphthol aralkyl type cyanate esterresin represented by the formula (16). An absorption of a cyanate estergroup was confirmed around 2264 cm⁻¹ in an infrared absorption spectrum.Further, a structure was identified by 13C-NMR and 1H-NMR. Theconversion rate of from OH groups to OCN groups was 99% or higher.

Synthetic Example 4 Synthesis of α-Naphthol Aralkyl Type Cyanate EsterResin

An α-naphthol aralkyl type cyanate ester resin was synthesized in thesame manner as in Synthetic Example 3 except that 103 g (OH group 0.47mol) of the α-naphthol aralkyl resin (SN485, OH group equivalent: 219g/eq., softening point: 86° C., supplied by Nippon Steel Chemical Co.,Ltd.) was replaced with 102 g (OH group 0.45 mol) of an α-naphtholaralkyl resin (SN4105, OH group equivalent: 226 g/eq., softening point:105° C., supplied by Nippon Steel Chemical Co., Ltd.) and that theamount of the cyanogen chloride was changed from 0.93 mol to 0.90 mol.The conversion rate of from OH groups to OCN groups was 99% or higher.

Example 1

70 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation) and 0.05 part by weight of zinc octylatewere mixed. The mixture was diluted with methyl ethyl ketone, to obtaina varnish having a resin solid content concentration of 65%. Table 1shows the evaluation results of the shelf life at low temperature of thevarnish.

Example 2

80 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 12 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation) and 0.05 part by weight of zinc octylatewere mixed. The mixture was diluted with methyl ethyl ketone, to obtaina varnish having a resin solid content concentration of 65%. Table 1shows the evaluation results of the shelf life at low temperature of thevarnish.

Example 3

70 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation) and 0.05 part by weight of zinc octylatewere mixed. The mixture was diluted with methyl ethyl ketone, to obtaina varnish having a resin solid content concentration of 65%. Table 1shows the evaluation results of the shelf life at low temperature of thevarnish.

Example 4

60 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (EXA-9900,supplied by DIC Corporation), 5 parts by weight of triallyl isocyanurate(TAIC), 5 parts by weight of triallyl cyanurate (TAC) and 0.05 part byweight of zinc octylate were mixed. The mixture was diluted with methylethyl ketone, to obtain a varnish having a resin solid contentconcentration of 65%. Table 1 shows the evaluation results of the shelflife at low temperature of the varnish.

Comparative Example 1

70 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.)and 0.05 part by weight of zinc octylate were mixed. The mixture wasdiluted with methyl ethyl ketone, to obtain a varnish having a resinsolid content concentration of 65%. Table 2 shows the evaluation resultsof the shelf life at low temperature of the varnish.

Comparative Example 2

80 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 12 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.)and 0.05 part by weight of zinc octylate were mixed. The mixture wasdiluted with methyl ethyl ketone, to obtain a varnish having a resinsolid content concentration of 65%. Table 2 shows the evaluation resultsof the shelf life at low temperature of the varnish.

Comparative Example 3

70 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.)and 0.05 part by weight of zinc octylate were mixed. The mixture wasdiluted with methyl ethyl ketone, to obtain a varnish having a resinsolid content concentration of 65%. Table 2 shows the evaluation resultsof the shelf life at low temperature of the varnish.

Comparative Example 4

60 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),5 parts by weight of triallyl isocyanurate (TAIC), 5 parts by weight oftriallyl cyanurate (TAC) and 0.05 part by weight of zinc octylate weremixed. The mixture was diluted with methyl ethyl ketone, to obtain avarnish having a resin solid content concentration of 65%. Table 2 showsthe evaluation results of the shelf life at low temperature of thevarnish.

Example 5

70 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation), 0.05 part by weight of zinc octylate and0.1 part by weight of di-t-butylhydroxytoluene (supplied by KawaguchiChemical Industry Co., LTD.) were mixed. The mixture was diluted withmethyl ethyl ketone, to obtain a varnish having a resin solid contentconcentration of 65%. Table 3 shows the evaluation results of the shelflife at normal temperature of the varnish.

Example 6

70 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 10 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 15 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation) and 0.05 part by weight of zinc octylatewere mixed. The mixture was diluted with methyl ethyl ketone, to obtaina varnish having a resin solid content concentration of 65%. The varnishwas stored in a cold insulation storehouse at 5° C. for 2 weeks. Then,the varnish was impregnated into an E glass cloth having a thickness of0.08 mm (IPC No. -#3313) and the varnish-impregnated glass cloth wasdried under heat at 160° C. for 8 minutes, whereby prepregs having aresin amount of 55% by weight were obtained. Eight prepregs having aresin amount 55%, obtained above, were stacked. 18 μm copper foils(3EC-HTE, supplied by Mitsui Mining & Smelting Co., LTD.) were disposedon both sides of the stacked prepregs, one copper foil on each side. Thecopper foils and the prepregs were vacuum-pressed under a pressure of 30kg/cm² at a temperature of 210° C. for 150 minutes, to obtain an 18μm-copper-clad laminate having a thickness of 0.8 mm. Table 4 shows thevalues of physical properties of the above copper-clad laminate.

Example 7

64 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation), 18 parts by weight of cyclophosphazenehaving a cyano group (FP-300, supplied by FUSHIMI Pharmaceutical Co.,LTD.), 50 parts by weight of a spherical silica (SC2050, averageparticle diameter 0.5 μm, supplied by Admatechs Company Limited), 5parts by weight of triallyl cyanurate (TAC) and 0.05 part by weight ofzinc octylate were mixed. The mixture was diluted with methyl ethylketone, to obtain a varnish having a resin solid content concentrationof 65%. A copper-clad laminate was obtained in the same manner as inExample 6 except that this varnish was used in place of the varnish usedin Example 6. Table 4 shows the values of physical properties of thecopper-clad laminate.

Example 8

67 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 4 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 3 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 10 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (EXA-9900,supplied by DIC Corporation), 16 parts by weight of a brominatedpolycarbonate resin (FG8500, supplied by TEIJIN Chemicals LTD.), 50parts by weight of a spherical synthetic silica (SC2050, averageparticle diameter 0.5 μm, supplied by Admatechs Company Limited) and0.05 part by weight of zinc octylate were mixed. The mixture was dilutedwith methyl ethyl ketone, to obtain a varnish having a resin solidcontent concentration of 65%. A copper-clad laminate was obtained in thesame manner as in Example 6 except that this varnish was used in placeof the varnish used in Example 6. Table 4 shows the values of physicalproperties of the copper-clad laminate.

Example 9

71 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (EXA-9900,supplied by DIC Corporation), 16 parts by weight of a brominatedpolycarbonate resin (FG8500, supplied by TEIJIN Chemicals LTD.), 25parts by weight of a spherical silica (SC2050, average particle diameter0.5 μm, supplied by Admatechs Company Limited) and 0.06 part by weightof zinc octylate were mixed. The mixture was diluted with methyl ethylketone, to obtain a varnish having a resin solid content concentrationof 65%. A copper-clad laminate was obtained in the same manner as inExample 6 except that this varnish was used in place of the varnish usedin Example 6. Table 4 shows the values of physical properties of thecopper-clad laminate.

Example 10

71 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (EXA-9900,supplied by DIC Corporation), 16 parts by weight of a brominatedpolycarbonate resin (FG8500, supplied by TEIJIN Chemicals LTD.), 30parts by weight of a mesoporous silica (MSF-01P, average particlediameter 1.3 μm, supplied by Admatechs Company Limited) and 0.05 part byweight of zinc octylate were mixed. The mixture was diluted with methylethyl ketone, to obtain a varnish having a resin solid contentconcentration of 65%. A copper-clad laminate was obtained in the samemanner as in Example 6 except that this varnish was used in place of thevarnish used in Example 6. Table 4 shows the values of physicalproperties of the copper-clad laminate.

Example 11

60 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 3 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 9 parts by weight of anaphthalene-skeleton-modified novolak type epoxy resin (HP-5000,supplied by DIC Corporation), 18 parts by weight of a cyclophosphazenehaving a cyano group (FP-300, supplied by FUSHIMI Pharmaceutical Co.,LTD.), 70 parts by weight of a spherical silica (SC2050, averageparticle diameter 0.5 μm, supplied by Admatechs Company Limited), 5parts by weight of triallyl isocyanurate (TAIC) and 0.05 part by weightof zinc octylate were mixed. The mixture was diluted with methyl ethylketone, to obtain a varnish having a resin solid content concentrationof 65%. Further, the varnish was weighed in a separable flask having astirrer, and methyl ethyl ketone was added to the varnish such that asolid content concentration became 20% by weight. The resultant mixturewas heated at 60° C. and stirred for 1 hour, to prepare a resincomposition solution. The thus-obtained solution was stored in a coldinsulation storehouse at 5° C. for 2 weeks. Then, the solution wasapplied to a mat surface of an 18 μm electrolytic copper foil (3EC-HTE:supplied by Mitsui Mining & Smelting Co., LTD.) with a doctor blade (gap200 μm). The applied solution was air-dried at room temperature for 10minutes and then dried with an air blowing dryer at 50° C. for 20minutes, whereby copper-foil-attached resin sheets having a resin layerthickness of about 15 μm each were obtained. The copper-foil-attachedresin sheets were disposed on the upper and lower sides of an etchedcore material having a thickness of 0.8 mm (CCL-EL190T, supplied byMitsubishi Gas Chemical Co., Inc.), one resin sheet on each side, andthe resin sheets and the core material were vacuum-pressed under apressure of 30 kg/cm² at a temperature of 210° C. for 150 minutes, toobtain a resin-sheet-attached 18 μm-copper-clad laminate having athickness of 0.85 mm. Table 4 shows the values of physical properties ofthe above copper-clad laminate.

Comparative Example 6

60 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 3 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 9 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),18 parts by weight of a cyclophosphazene having a cyano group (FP-300,supplied by FUSHIMI Pharmaceutical Co., LTD.), 70 parts by weight of aspherical silica (SC2050, average particle diameter 0.5 μm, supplied byAdmatechs Company Limited), 5 parts by weight of triallyl isocyanurate(TAIC) and 0.05 part by weight of zinc octylate were mixed. The mixturewas diluted with methyl ethyl ketone, to obtain a varnish having a resinsolid content concentration of 65%. A copper-clad laminate was obtainedin the same manner as in Example 6 except that this varnish was used inplace of the varnish used in Example 6. Table 5 shows the values ofphysical properties of the copper-clad laminate.

Comparative Example 7

64 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),18 parts by weight of a cyclophosphazene having a cyano group (FP-300,supplied by FUSHIMI Pharmaceutical Co., LTD.), 50 parts by weight of aspherical silica (SC2050, average particle diameter 0.5 μm, supplied byAdmatechs Company Limited), 5 parts by weight of triallyl cyanurate(TAC) and 0.05 part by weight of zinc octylate were mixed. The mixturewas diluted with methyl ethyl ketone, to obtain a varnish having a resinsolid content concentration of 65%. A copper-clad laminate was obtainedin the same manner as in Example 6 except that this varnish was used inplace of the varnish used in Example 6. Table 5 shows the values ofphysical properties of the copper-clad laminate.

Comparative Example 8

67 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 4 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 3 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 10 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),16 parts by weight of a brominated polycarbonate resin (FG8500, suppliedby TEIJIN Chemicals LTD.), 50 parts by weight of a spherical syntheticsilica (SC2050, average particle diameter 0.5 μm, supplied by AdmatechsCompany Limited) and 0.05 part by weight of zinc octylate were mixed.The mixture was diluted with methyl ethyl ketone, to obtain a varnishhaving a resin solid content concentration of 65%. A copper-cladlaminate was obtained in the same manner as in Example 6 except thatthis varnish was used in place of the varnish used in Example 6. Table 5shows the values of physical properties of the copper-clad laminate.

Comparative Example 9

71 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),16 parts by weight of a brominated polycarbonate resin (FG8500, suppliedby TEIJIN Chemicals LTD.), 25 parts by weight of a spherical silica(SC2050, average particle diameter 0.5 μm, supplied by Admatechs CompanyLimited) and 0.05 part by weight of zinc octylate were mixed. Themixture was diluted with methyl ethyl ketone, to obtain a varnish havinga resin solid content concentration of 65%. A copper-clad laminate wasobtained in the same manner as in Example 6 except that this varnish wasused in place of the varnish used in Example 6. Table 5 shows the valuesof physical properties of the copper-clad laminate.

Comparative Example 10

71 parts by weight of the vinyl compound “B” (number average molecularweight 2,250, vinyl group equivalent 1,189 g/vinyl group) obtained inSynthetic Example 1, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 5 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 3 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),16 parts by weight of a brominated polycarbonate resin (FG8500, suppliedby TEIJIN Chemicals LTD.), 30 parts by weight of a mesoporous silica(MSF-01P, average particle diameter 1.3 μm, supplied by AdmatechsCompany Limited) and 0.05 part by weight of zinc octylate were mixed.The mixture was diluted with methyl ethyl ketone, to obtain a varnishhaving a resin solid content concentration of 65%. A copper-cladlaminate was obtained in the same manner as in Example 6 except thatthis varnish was used in place of the varnish used in Example 6. Table 5shows the values of physical properties of the copper-clad laminate.

Comparative Example 11

60 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 5 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 244 g/eq.) obtained inSynthetic Example 4, 3 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 9 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),18 parts by weight of a cyclophosphazene having a cyano group (FP-300,supplied by FUSHIMI Pharmaceutical Co., LTD.), 65 parts by weight of aspherical silica (SC2050, average particle diameter 0.5 μm, supplied byAdmatechs Company Limited), 5 parts by weight of triallyl isocyanurate(TAIC) and 0.06 part by weight of zinc octylate were mixed. The mixturewas diluted with methyl ethyl ketone, to obtain a varnish having a resinsolid content concentration of 65%. A resin-sheet-attached copper-cladlaminate was obtained in the same manner as in Example 11 except thatthis varnish was used in place of the varnish used in Example 11. Table5 shows the values of physical properties of the resin-sheet-attachedcopper-clad laminate.

Comparative Example 12

67 parts by weight of the vinyl compound “D” (number average molecularweight 1,187, vinyl group equivalent 590 g/vinyl group) obtained inSynthetic Example 2, 4 parts by weight of the naphthol aralkyl typecyanate ester resin (cyanate equivalent: 237 g/eq.) obtained inSynthetic Example 3, 3 parts by weight of bismaleimide (BMI-70, suppliedby Nippon Kayaku Co., Ltd.), 10 parts by weight of a biphenyl aralkyltype novolak epoxy resin (NC3000H, supplied by Nippon Kayaku Co., Ltd.),16 parts by weight of a brominated polycarbonate resin (FG8500, suppliedby TEIJIN Chemicals LTD.), 50 parts by weight of a spherical syntheticsilica (SC2050, average particle diameter 0.5 μm, supplied by AdmatechsCompany Limited) and 0.05 part by weight of zinc octylate were mixed.The mixture was diluted with methyl ethyl ketone, to obtain a varnishhaving a resin solid content concentration of 65%. A copper-cladlaminate was obtained in the same manner as in Example 6 except thatthis varnish was used immediately after its preparation without 2-weekstorage at 5° C. Table 6 shows the values of physical properties of thecopper-clad laminate.

TABLE 1 Shelf life of varnish Example Example Example Example at lowtemperature 1 2 3 4 Appearance Immediately Trans- Trans- Trans- Trans-of varnish after parent parent parent parent preparation After 2 weeksTrans- Trans- Trans- Trans- parent parent parent parent

TABLE 2 Shelf life of varnish at low temperature CEx. l CEx. 2 CEx. 3CEx. 4 Appearance Immediately Trans- Trans- Trans- Trans- of varnishafter parent parent parent parent preparation After 2 weeks CloudyLightly Cloudy Cloudy cloudy CEx. = Comparative Example

TABLE 3 Shelf life of varnish at normal temperature Example 1 Example 5Generation Immediately after No No of high preparation molecular After 4weeks Yes no weight compound

TABLE 4 Evaluation results of copper-clad laminate Ex. 6 Ex. 7 Ex. 8 Ex.9 Ex. 10 Ex. 11 Dielectric constant (10 GHz) 3.8   3.6   3.6   3.4  3.4   Not measured Dielectric loss tangent 0.0060 0.0055 0.0060 0.00500.0050 Not (10 GHz) measured Peel strength ∘ ∘ ∘ ∘ ∘ ∘ (Spec.: >0.7kg/cm) Heat resistance after moisture ∘∘∘∘ ∘∘∘∘ ∘∘∘∘ ∘∘∘∘ ∘∘∘∘ ∘∘∘∘absorption PCT-4 hours 288° C./30 second immersion Ex. = Example

TABLE 5 Evaluation results of copper-clad laminate CEx. 6 CEx. 7 CEx. 8CEx. 9 CEx. 10 CEx. 11 Dielectric constant (10 GHz) 3.8 3.6 3.6 3.4 3.4Not measured Dielectric loss tangent 0.0060 0.0055 0.0060 0.0050 0.0050Not (10 GHz) measured Peel strength x x x x x x (Spec.: 0.7 kg/cm) Heatresistance after moisture ∘xxx ∘∘xx ∘xxx ∘∘xx ∘∘xx ∘xxx absorption PCT-4hours 288° C./30 second immersion CEx. = Comparative Example

TABLE 6 Evaluation results of Comparative copper-clad laminate Example12 Dielectric constant (10 GHz) 3.6 Dielectric loss tangent (10 GHz)0.0060 Peel strength (Spec.: >0.7 kg/cm) ∘ Heat resistance aftermoisture ∘∘∘∘ absorption PCT-4 hours 288° C./30 second immersion

(Measurement Methods)

1) A number average molecular weight and a weight average molecularweight were obtained by a gel permeation chromatography (GPC) method.Data processing was carried out based on the GPC curve and molecularweight calibration curve of a sample. The molecular weight calibrationcurve was obtained by making an approximation of a relation between themolecular weight of a standard polystyrene and an elution time with thefollowing equation, Log M=A₀X³+A₁X²+A₂X+A₃+A₄/X², wherein M is amolecular weight, X is an elution time—19 (minute) and A is acoefficient.

2) A hydroxyl group equivalent was determined from an absorptionintensity at 3,600 cm⁻¹ in an IR analysis (solution cell method; cellthickness=1 mm) in which 2,6-dimethylphenol was used as a standardreference material and dry dichloromethane was used as a solvent.

3) A vinyl group equivalent was determined from an absorption intensityat 910 cm⁻¹ in an IR analysis (solution cell method; cell thickness=1mm) in which 1-octene was used as a standard reference material andcarbon disulfide was used as a solvent.

4) A cyanate equivalent was determined as follows. The absorption of acyanate ester group around 2264 cm⁻¹ in an infrared absorption spectrumwas confirmed, then a structure was identified by 13C-NMR and 1H-NMR anda conversion rate of from OH groups into OCN groups was measured. Thecyanate equivalent was calculated on the basis of the conversion ratefrom the OH equivalent of a naphthol aralkyl resin used for evaluation.

5) Shelf Life of Varnish at Low Temperature

A varnish was placed in a 300 cc glass sample bottle and the varnish wasobserved for transparency (turbidity) by visual observation. Then, thevarnish was stored in a cold insulation storehouse at 5° C. for 2 weeks.Then, the varnish was again observed for transparency (turbidity) byvisual observation. (n=1).

6) Shelf Life of Varnish at Normal Temperature

Measurements of a varnish were carried out on the basis of a GPC methodimmediately after its preparation and after leaving the varnish to standfor 4 weeks at room temperature (25° C.). “Yes” represents theappearance of a peak which showed the generation of a high molecularweight compound in a chart. “No” represents that a peak showing thegeneration of a high molecular weight compound did not appear.

7) Peel Strength

An 18 μm-copper-foil-attached specimen (30 mm×150 mm×0.8 mm) wasmeasured for the peel strength of a copper foil two times in conformitywith JIS C6481. An average value of at least 0.7 kg/cm in the two-timemeasurements was regarded as “Passing” (O) and an average value of lessthan 0.7 kg/cm was regarded as “Not passing” (x). (n=2).

8) Dielectric Constant and Dielectric Loss Tangent

A specimen of a copper-clad laminate having a thickness of 0.8 mm, fromwhich a copper foil had been removed, was measured for a dielectricconstant and a dielectric loss tangent at 10 GHz by a cavity resonatorperturbation method (Agilent 8722ES, supplied by Agilent technologies).(n=1).

9) Heat Resistance after Moisture Absorption

A 5 cm×5 cm sample (n=4) obtained by etching a copper foil of an 18μm-copper-foil-attached laminate having a thickness of about 0.8 mm wasdried at 115° C. for 20 hours, then treated with a pressure cookertester (supplied by Hirayama Manufacturing Corporation, PC-3 type) at121° C. at 2 atmospheric pressure for 4 hours, and then immersed in asolder bath at 288° C. for 30 seconds. Four samples were observed forthe presence or absence of swelling by visual observation, respectively.“o” represents no defect. “x” represents the occurrence of swelling.

What is claimed is:
 1. A prepreg obtained by impregnating a resincomposition into a glass woven fabric and semi-curing theresin-composition-impregnated glass woven fabric, wherein the resincomposition contains a vinyl compound (a) represented by the formula(1), a maleimide compound (b) represented by the formula (5), a cyanateester resin (c) represented by the formula (6) and an epoxy resin (d)having a repeating structure of the formula (7),

wherein —(O—X—O)— is a structure defined by the formula (2) or theformula (3), —(Y—O)— is an arrangement of a structure defined by theformula (4) or a random arrangement of at least two kinds of structuresdefined by the formula (4), and each of a and b is an integer of 0 to100, provided that at least one of a and b is not 0,

wherein R₁, R₂, R₃, R₇ and R₈ are the same or different and represent ahalogen atom, an alkyl group having 6 or less carbon atoms or a phenylgroup, R₄, R₅ and R₆ are the same or different and represent a hydrogenatom, a halogen atom, an alkyl group having 6 or less carbon atoms or aphenyl group,

wherein R₁₇ and R₁₈ are the same or different and represent a halogenatom, an alkyl group having 6 or less carbon atoms or a phenyl group,and R₁₉ and R₂₀ are the same or different and represent a hydrogen atom,a halogen atom, an alkyl group having 6 or less carbon atoms or a phenylgroup,

wherein Z represents an organic group having 200 or less carbon atomswhich may contain at least one member selected from the group consistingof an oxygen atom, a sulfur atom, a phosphorus atom and a nitrogen atom,and c is an integer of 2 to 20,

wherein R represents a hydrogen atom or a methyl group and n is from 1to 10,

wherein R₂₁ represents an alkyl group having 1 to 6 carbon atoms, R₂₂represents an alkyl group having 1 to 6 carbon atoms or an alkoxy grouphaving 1 to 6 carbon atoms, B is a direct bond or an alkylene grouphaving 1 to 6 carbon atoms, and m is from 1 to 10; and wherein an amountof vinyl compound (a) is in a range of from 50-80 parts by weight basedon 100 parts by weight of a resin solid content of the resincomposition.
 2. The prepreg according to claim 1, wherein the resincomposition which is thermally molten is impregnated into the glasswoven fabric.
 3. The prepreg according to claim 1, wherein a varnishcomprising the resin composition and an organic solvent is impregnatedinto the glass woven fabric.
 4. A metal-foil-clad laminate obtained bydisposing metal foil(s) on one surface or both surfaces of a stack of atleast one prepreg as defined in claim 1 and laminate-molding theresultant stack.
 5. A resin sheet obtained by applying a varnishcomprising the resin composition defined in claim 1 and an organicsolvent to a surface of a metal foil or a film and drying the appliedvarnish.